In a conventional manner, the treatments of water use natural granular materials such as sands or gravels, expensive or inexpensive clays, activated carbon, either reconstituted or not, and other mineral products. These materials are selected as a function of the treatment intended, in order to fix micro-organisms in the case of biological treatment, or to physically trap the materials in suspension in the case of filtration treatments. The interest in these materials is related to their availability and their low cost, but they are not well adapted to these treatments, and the processes for carrying out the treatments are rather deficient and poorly performing, especially for biological treatments with fixed biomasses.
French Pat. No. 83.07186 describes a composite material for biological treatment. This material is formed of thermoplastic matrices of an essentially cylindrical form, on the surface of which have been fixed adsorbent particles of activated carbon. This material has essentially the same properties for micro-organism fixation as the activated carbon, but differs by an improved mechanical strength. However, this material remains sensitive to the phenomena of attrition and is only adapted to a single type of biological treatment, treatment in a fixed bed, either immersed or by flowing therethrough. It should be noted that, by expansion of the synthetic matrix, it is possible to modulate the density of the material, however this expansion is very difficult in practice to control and the size of the particles is related to the degree of expansion and this is not adjustable independently of the density. Further, such a material lends itself poorly to cleaning operations in view of the elimination of the fixed biomass.
The present invention provides a new material for the treatment of water, having volume and surface properties which are improved with respect to existing materials.
One object of the invention is to provide a process for manufacturing such a granular material which permits adjusting the characteristics thereof as a function of the intended manner of use, in such a manner that the material may be optimized hydrodynamically and for material transfer.
In particular, the invention permits carrying out water treatments, either in a fixed bed, or in a turbulent bed or in a fluidized bed.
Another object of the invention is to improve the efficiency of the material with respect to known materials--the fixation efficiency of micro-organisms in the case of biological treatments, and efficiency of physico-chemical retention in the case of filtrations.
Another object of the invention is to provide a material lending itself to easy and economical washings or cleanings.
A further object of the invention is to provide a material having improved mechanical properties with respect to the composite material of activated carbon described above, making the material in particular insensitive to the phenomena of attrition.